Motion vector refining apparatus

ABSTRACT

A motion vector refining apparatus including a control unit, N filter units, and a mixer unit is provided. The control unit receives a motion estimation signal generated by a motion estimation unit and calculates a plurality of variation parameters according to a current motion vector, surrounding motion vectors, or a block matching error, so as to generate a control signal. The N filter units respectively calculate N filtering motion vectors by using N analysis processes. The mixer unit weights and mixes the filtering motion vectors according to the control signal to adjust and output a refined motion vector. Thereby, the motion vector refining apparatus can detect the edge of a moving object and mix filtering results of the analysis processes to adjust and refine motion vectors, so as to reduce image defects caused by a smooth processing.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the priority benefit of Taiwan applicationserial no. 100116697, filed on May 12, 2011. The entirety of theabove-mentioned patent application is hereby incorporated by referenceherein and made a part of this specification.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention generally relates to a motion estimation and compensationtechnique, and more particularly, to a motion vector refining apparatuswhich can increase vertical resolution of an image.

2. Description of Related Art

Existing image display techniques usually adopt an interlace scan mode(usually applied to cathode ray tube (CRT) TVs) and a progressive scanmode (usually applied to digital TVs or digital cinemas). In theinterlace scan mode, only half of the scan lines in an image aretransmitted or played each time (i.e., scan lines in odd numbers(referred to as an odd field) and scan lines in even numbers (referredto as an even field) in the image are alternatively played). Since eachfield only contains data of the scan lines in odd or even numbers,vertical discontinuity is produced in a displayed image. Contrarily, inthe progressive scan mode, the scan lines in an image are played one byone. However, the frame rate in the progressive scan mode is usuallymuch lower than that in the interlace scan mode. Accordingly, imagediscontinuity or motion blur may be produced in a displayed image.

In order to increase image resolution and smoothness and avoid imagediscontinuity and motion blur, conventionally, a “motion adaptivedeinterlacing” technique is adopted to increase the vertical resolutionin a motion image in the interlace scan mode. In recent years, a “motioncompensated deinterlacing” technique is further adopted to increase thevertical resolution of an image. In the motion compensated deinterlacingtechnique, the motion trajectory of a moving object in an image ispredicted, and new pixel data is interpolated on the motion trajectory,so that the lost field can be effectively compensated and the resolutionin the vertical direction can be effectively retained. Accordingly,image motion is made very clear and image blur is avoided. Regarding theprogressive scan mode with lower frame vertical resolution, the lostpart of an image can be interpolated on the time axis through thetechnique described above, so that the vertical resolution of the outputimage signal can be increased.

In the motion compensated deinterlacing technique, in order to make themotion vectors of the same moving object to be distributed moreconsistently, a smooth processing is performed on the motion vectors ofneighboring macroblocks to reduce the variations of the motion vectors.However, motion vector estimation error, and accordingly image defects(for example, halation), may be produced when the smooth processing isperformed at where the images of two moving objects meet each other orat the edges of dynamic and static areas. Thereby, an estimation andcompensation technique for refining motion vectors is desired.

SUMMARY OF THE INVENTION

Accordingly, the invention is directed to a motion vector refiningapparatus which can detect the discontinuous edge portions of a movingobject and control a filtering condition of motion vectors accordingly,so as to reduce image defects caused by a smooth processing.

The invention provides a motion vector refining apparatus including acontrol unit, N filter units, and a mixer unit, wherein N is a positiveinteger and is greater than 1. The control unit receives a motionestimation signal generated by a motion estimation unit, wherein themotion estimation signal includes a plurality of total motion vectors,and the total motion vectors include a current motion vectorcorresponding to a current macroblock and a plurality of surroundingmotion vectors. The control unit calculates a variation parameteraccording to the current motion vector and the surrounding motionvectors, so as to generate a control signal. The N filter unitsrespectively analyze the total motion vectors by using N analysisprocesses, so as to generate N filtering motion vectors. The mixer unitis coupled to the control unit and the filter units. The mixer unitweights and mixes the filtering motion vectors according to the controlsignal, so as to adjust and output a refined motion vector.

According to an embodiment of the invention, the motion estimationsignal further includes a block matching error corresponding to thecurrent macroblock, and the control unit includes a variation parametercalculation unit and a reliability parameter analysis unit. Thevariation parameter calculation unit performs a motion vectorcorrelation calculation by using variations of the current motion vectorand the surrounding motion vectors corresponding to a plurality ofneighboring macroblocks, so as to calculate the variation parameter. Thereliability parameter analysis unit receives and analyzes the blockmatching error to generate a reliability parameter, wherein the blockmatching error is an optimal result generated by performing blockmatching on the current macroblock and a plurality of macroblocks of anext frame. The value mixer is coupled to the variation parametercalculation unit and the reliability parameter analysis unit. The valuemixer calculates and generates the control signal according to a mixingproportion, the variation parameter, and the reliability parameter.

According to an embodiment of the invention, the analysis processes ofthe filter units may be N different smooth intensities. Besides, themixer unit adjusts N weighted values according to the control signal andadds up the product of the i^(th) weighted value and the i^(th)filtering motion vector, so as to generate the refined motion vector,wherein i is a positive integer and 1≦i≦N.

According to an embodiment of the invention, the control unit includes Nvariation parameter calculation units and a selector. The i^(th)variation parameter calculation unit performs a motion vectorcorrelation calculation by using the i^(th) filtering motion vector andthe surrounding motion vectors corresponding to a plurality ofneighboring macroblocks around the current macroblock, so as tocalculate an i^(th) variation parameter. The selector is coupled to thevariation parameter calculation units. The selector determines thevalues of the variation parameters to generate the control signal.

According to an embodiment of the invention, the mixer unit may be amultiplexer. The multiplexer outputs a selected filtering motion vectoraccording to the control signal. Besides, the refined motion vector isoutput to the motion estimation unit to adjust the total motion vectors,or the refined motion vector is output to a motion compensation unit toperform a motion compensation operation.

As described above, the motion vector refining apparatus provided by anembodiment of the invention calculates variation parameters of motionvectors and analyzes a block matching error of macroblocks, so as todetermine whether an output image is at the edge of a moving object andadjust and refine motion vectors output by a plurality of filter units.Thereby, when an image is at the edge of a moving object, the motionvector refining apparatus can reduce smooth intensities of the motionvectors (i.e., allow the motion vectors to have greater variations).When the motion vectors require higher smooth intensities (for example,the processed macroblock or pixel is not at the edge of the movingobject), the motion vector refining apparatus adjusts and outputs motionvectors with high smooth intensities, so as to reduce image defectscaused by a smooth processing.

These and other exemplary embodiments, features, aspects, and advantagesof the invention will be described and become more apparent from thedetailed description of exemplary embodiments when read in conjunctionwith accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings are included to provide a furtherunderstanding of the invention, and are incorporated in and constitute apart of this specification. The drawings illustrate embodiments of theinvention and, together with the description, serve to explain theprinciples of the invention.

FIG. 1A is a schematic block diagram of an image motion vectorestimation and compensation system.

FIG. 1B is a diagram illustrating how to interpolate a new field on amotion trajectory by using an image motion vector estimation andcompensation algorithm.

FIG. 2A is a block diagram of an image motion vector estimation andcompensation system according to an embodiment of the invention.

FIG. 2B is a block diagram of an image motion vector estimation andcompensation system according to another embodiment of the invention.

FIG. 3 is a block diagram of a motion vector refining apparatusaccording to a first embodiment of the invention.

FIG. 4A is a block diagram of a control unit in FIG. 3.

FIG. 4B is a diagram illustrating how to calculating reliabilityinformation by using a current macroblock.

FIG. 5 is a block diagram of a variation parameter calculation unit inFIG. 4A.

FIG. 6 is a graph illustrating how a mixer unit generates weightedvalues W1 and W3 according to a value CSV of a control signal.

FIG. 7 is a block diagram of a motion vector refining apparatusaccording to a second embodiment of the invention.

FIG. 8 is a block diagram of a control unit in FIG. 7.

DESCRIPTION OF THE EMBODIMENTS

Reference will now be made in detail to the present preferredembodiments of the invention, examples of which are illustrated in theaccompanying drawings. Wherever possible, the same reference numbers areused in the drawings and the description to refer to the same or likeparts.

FIG. 1A is a schematic block diagram of an image motion vectorestimation and compensation system 100. The present embodiment isapplicable to an image standard in the interlace scan mode or theprogressive scan mode. In the present embodiment, the image signal 102in FIG. 1A is assumed to be in the interlace scan mode. Referring toFIG. 1A, the motion estimation unit 110 receives the image signal 102,estimates the motion trajectory of a moving object in the image signal102, generates an motion estimation signal 112, and outputs the motionestimation signal 112 to the motion compensation unit 120. The motionestimation signal 112 contains image information in unit of macroblockand corresponding motion vector information.

FIG. 1B is a diagram illustrating how to interpolate a new field NF on amotion trajectory by using an image motion vector estimation andcompensation algorithm. The motion estimation unit 110 performs multipleblock matching operations by using an image motion vector estimationalgorithm according to a current macroblock MB0 in the field F1 of theimage signal 102 and a plurality of macroblocks MB in the field F2 ofthe image signal 102, and the motion estimation unit 110 calculates themotion estimation signal 112 by using the current macroblock MB0 (in thefield F1) and the macroblock MB5 (in the field F2) with the optimalblock matching result. To be specific, after the motion estimation unit110 calculates the block matching errors between the current macroblockMB0 and a plurality of macroblocks MB in the field F2, the smallestblock matching error is considered the “optimal block matching result”(i.e., in the present embodiment, the current macroblock MB0 and themacroblock MB5 have the smallest pixel difference). Thus, the motionestimation signal 112 contains a motion vector and a block matchingerror corresponding to each macroblock.

The motion compensation unit 120 interpolates pixels between scan linesin the macroblock NMB on the motion trajectory by using the currentmacroblock MB0 and the macroblock MB5. Namely, the motion compensationunit 120 interpolates a new field NF by using the current macroblockMB0, a current motion vector MV0 (not shown), and the macroblock MB5through the motion compensated deinterlacing technique, so as tocompensate the lost field effectively and increase the verticalresolution of the output image signal 122. In the present embodiment,the lost part of an image in the progressive scan mode can also beinterpolated by using the technique described above (i.e., the imagesignal 102 in FIG. 1 is in the progressive scan mode), so as to increasethe frame rate of the output image signal 122.

In the image motion vector estimation and compensation algorithm,because the motion vectors generated through estimation may be slightlydifferent from each other in the same moving object, a smooth processingis performed on motion vectors of neighboring macroblocks through somestatistical algorithms or filtering algorithms, so as to increase thecorrelation between these motion vectors. For example, neighboringmotion vectors are low-pass filtered by using a low-pass filter.

However, discontinuity between motion vectors may be produced at theedge of a moving object in an image (i.e., the correlation betweenmotion vectors of neighboring macroblocks is very low). Or, when thereis an irregularly moving area in an image (i.e., the block matchingerrors between macroblocks are large) and the smooth processing isperformed to all the motion vectors, unreliable motion vectors may beproduced and accordingly defects may be produced in the compensatedimage.

FIG. 2A is a block diagram of an image motion vector estimation andcompensation system 200 according to an embodiment of the invention, andFIG. 2B is a block diagram of an image motion vector estimation andcompensation system 201 according to another embodiment of theinvention. In the present embodiment, the motion vector refiningapparatus 210 performs variation parameter analysis on neighboringmotion vectors in the motion estimation signal 112 and performsreliability analysis on image data of neighboring macroblocks, so as toadjust and control the filtering condition of the motion vectors andallow the motion vectors at the edge of the moving object to be preciseand stable. Accordingly, the processed motion vector signal 212 can beused by the motion estimation unit 110 as a reference for estimatingother motion vectors (as indicated by the dotted line in FIG. 2A andFIG. 2B) or provided to the motion compensation unit 120 to performimage compensation operations (as shown in FIG. 2B).

FIG. 3 is a block diagram of a motion vector refining apparatus 210according to a first embodiment of the invention. The motion vectorrefining apparatus 210 includes a control unit 310, N filter units320_1-320_N, and a mixer unit 330, wherein N is a positive integer andis greater than 1. In the present embodiment, three filter units320_1-320_3 are taken as examples (i.e., N=3). However, the invention isnot limited thereto. In the present embodiment, the motion vectorrefining apparatus 210 further includes a buffer 340. The buffer 340receives and buffers the motion estimation signal 112 and outputs themotion estimation signal 112 to the control unit 310. In the presentembodiment, the motion estimation signal 112 contains a total motionvector TMV and a block matching error corresponding to each macroblock.The buffer 340 further respectively transmits the total motion vectorsTMV to the filter units 320_1-320_N. The control unit 310 receives themotion estimation signal 112 and performs variation parametercalculation and reliability analysis by using related information (forexample, variations of the current motion vector and the surroundingmotion vectors and the block matching error of the current macroblock)of the motion estimation signal 112, so as to generate a control signalCS.

The filter units 320_1-320_3 respectively calculate the total motionvectors TMV by using three different analysis processes, so as togenerate three filtering motion vectors FMV_1-FMV_3. Herein an “analysisprocess” may be the smooth intensity of a low-pass filter or acommonly-used statistical calculation (for example, histogram statistic,average statistic, or median statistic), and those skilled in the artshould be able to determine the number of the filter units 320_1-320_Nand the analysis processes thereof according to their own designrequirements. In the present embodiment, the filter units 320_1-320_Nare assumed to be low-pass filters having different smooth intensities.For example, the filter units 320_1, 320_2, and 320_3 are respectively a3-tap, a 5-tap, and a 9-tap low-pass filter, wherein a greater tapnumber indicates a higher correlation between motion vectors, a highersmooth intensity, and closer values between neighboring motion vectors.

Referring to FIG. 3 again, the mixer unit 330 is coupled to the controlunit 310 and the filter units 320_1-320_3. The mixer unit 330 weightsand mixes the filtering motion vectors FMV_1-FMV_3 according toinformation carried by the control signal CS, so as to output the motionvector signal 212. Or, the mixer unit 330 selects one of the filteringmotion vectors FMV_1-FMV_3 according to the control signal CS to outputthe motion vector signal 212. Those implementing the present embodimentcan control and adjust the filtering motion vectors FMV_1-FMV_3 by usingthe estimation result of the control unit 310 based on the spirit of theinvention.

Herein the operation, function, and structure of the control unit 310 inthe first embodiment will be described in detail. FIG. 4A is a blockdiagram of the control unit 310 in FIG. 3, and FIG. 4B is a diagramillustrating how to calculate reliability information by using thecurrent macroblock MB0. As shown in FIG. 4A and FIG. 4B, the controlunit 310 includes a motion vector buffer 430 and a reliabilityinformation buffer 440. The motion vector buffer 430 and the reliabilityinformation buffer 440 respectively receive the total motion vectors TMVof the motion estimation signal 112 and a block matching error 438calculated by the motion estimation unit 110. The motion vector buffer430 buffers the current motion vector MV0 corresponding to the currentmacroblock MB0 and the surrounding motion vectors MV1-MV4 correspondingto the neighboring macroblocks MB1-MB4 (as shown in FIG. 4B), and thereliability information buffer 440 buffers the block matching error 438corresponding to the current macroblock MB0.

In the present embodiment, the current motion vector MV0 and thesurrounding motion vectors MV1-MV4 are respectively the optimal motiontrajectories of the current macroblock MB0 and the neighboringmacroblocks MB1-MB4 from the field F1 to the field F2. Referring to FIG.4A, the variation parameter calculation unit 410 performs a motionvector correlation calculation (for example, a sum of absolutedifference (SAD) calculation) according to the motion vectors MV0-MV4,so as to analyze whether there is any large variation between thecurrent motion vector MV0 and the surrounding motion vectors MV1-MV4.FIG. 5 is a block diagram of the variation parameter calculation unit410 in FIG. 4A. In the present embodiment, the variation parametercalculation unit 410 receives the current motion vector MV0 and thesurrounding motion vectors MV1-MV4 and performs a SAD calculation byusing the absolute value subtractor 510 and the adder 520, so as tocalculate a variation parameter VP. In other words, in the presentembodiment, the variation parameter calculation unit 410 calculates thevariation parameter VP by using following formula (1):VP=(|MV0−MV1|+|MV0−MV2|+|MV0−MV3|+|MV0−MV4|)  (1)

However, the invention is not limited to foregoing formula (1), and inother embodiments, the motion vector correlation calculation may also bereplaced by a variance calculation in which the differences between themotion vectors are squared and added up.

In the present embodiment, the macroblocks MB1-MB4 above, below, to theleft of, and to the right of the current macroblock MB0 are consideredthe neighboring macroblocks of the current macroblock MB0, so as todefine the surrounding motion vectors MV1-MV4 of the current motionvector MV0. However, the surrounding motion vectors MV1-MV4 should bedefined according to the motion vector spatial correlation algorithm,and those implementing the present embodiment should determine the rangeof the surrounding motion vectors according to their designrequirements, so as to determine the method for calculating thevariation parameters adopted by the variation parameter calculation unit410. In other embodiments, the variation parameter calculation unit 410may also select the upper left, lower left, upper right, and lower rightmotion vectors around the current macroblock MB0 to calculate thevariation parameters.

The reliability parameter analysis unit 420 in FIG. 4A receives andanalyzes the block matching error 438 in the motion estimation signal112 and outputs a reliability parameter RP. As described above, theblock matching error 438 is the optimal block matching result generatedby performing block matching on the current macroblock MB0 and themacroblock MB5 of the next image. In the motion estimation signal 112generated by the motion estimation unit 110, the block matching error438 is the image similarity between the current macroblock MB0 and themacroblocks of the next image calculated through a mean absolutedifference (MAD) algorithm, a mean squared error (MSE) algorithm, or asum of absolute difference (SAD) algorithm. However, the presentembodiment is not limited thereto. In the present embodiment, a smallerblock matching error 438 indicates a more precise current motion vectorMV0 and a smaller reliability parameter RP. Contrarily, a greaterdifference between the current macroblock MB0 and the neighboringmacroblocks MB1-MB4 indicates a more inaccurate current motion vectorMV0 and a greater reliability parameter RP.

A value mixer 450 is coupled to the variation parameter calculation unit410 and the reliability parameter analysis unit 420. The value mixer 450mixes the variation parameter VP and the reliability parameter RPaccording to a mixing proportion SWD between the variation parameter VPand the reliability parameter RP, so as to generate the control signalCS. Those implementing the present embodiment can permanently store themixing proportion SWD in the value mixer 450 or manually adjust themixing proportion SWD (as indicated by the dotted line in FIG. 4A)according to their design requirements, so as to accomplish the spiritof the embodiment. In the present embodiment, the value mixer 450calculates the value CSV of the control signal CS by assuming the mixingproportion of the variation parameter VP to be 3 and the mixingproportion of the reliability parameter RP to be 1 (as indicated infollowing formula (2)):CSV=3×VP+1×RP  (2)

Referring to FIG. 3 again, the mixer unit 330 is coupled to the controlunit 310 and the filter units 230_1-320_3. The mixer unit 330 generatesthree weighted values W1-W3 according to the control signal CS. FIG. 6is a graph illustrating how the mixer unit 330 generates the weightedvalues W1 and W3 according to the value CSV of the control signal CS.The graphs of the weighted values W1 and W3 and the value CSV in FIG. 6can be generated based on experimental data, and the data used herein isonly used as reference.

As described above, the value CSV of the control signal CS is generatedby weighting and mixing the variation parameter VP and the reliabilityparameter RP. Thus, if the variation parameter VP has a large value(i.e., the spatial correlation between the motion vectors MV0-MV4 islow) and the reliability parameter RP also has a large value (i.e., nooptimal motion vector is found after performing block matchingestimation on the current macroblock MB0 in FIG. 4B) (as indicated byspot A in FIG. 6), there is a high possibility that the currentmacroblock MB0 is located at the edge of the moving object. In thiscase, the mixer unit 330 increases the weighted value W1 (for example,to a value a1) corresponding to the filter unit 320_1 (the 3-taplow-pass filter) which has a lower smooth intensity and reduces theweighted value W3 (for example, to a value a3) corresponding to thefilter unit 320_3 (the 9-tap low-pass filter) which has a higher smoothintensity, so as to reduce the correlation between the motion vectors.

Contrarily, if the variation parameter VP has a small value (i.e., thereis a high correlation between the motion vectors) and the reliabilityparameter RP also has a small value (i.e., an optimal motion vector isfound after performing block matching estimation on the currentmacroblock MB0 in FIG. 4B) (as indicated by spot B in FIG. 6), thecurrent macroblock MB0 is located within the moving object or in a samemoving object. In this case, the mixer unit 330 reduces the weightedvalue W1 (for example, to a value b1) corresponding to the filter unit320_1 (the 3-tap low-pass filter) which has a lower smooth intensity andincreases the weighted value W3 (for example, to a value b3)corresponding to the filter units 320_3 (the 9-tap low-pass filter)which has a higher smooth intensity, so as to make neighboring motionvectors close to each other and achieve a smooth effect.

Thereby, after the mixer unit 330 in FIG. 3 generates a refined motionvector RMV by using following formula (3), the mixer unit 330 adjuststhe refined motion vector RMV into the motion vector signal 212 andoutputs the motion vector signal 212:RMV=W1×FMV_(—)1+W2×FMV_(—)2+W3×FMV_(—)3  (3)

Another embodiment of the invention will be further described hereinwith reference to FIG. 7. FIG. 7 is a block diagram of a motion vectorrefining apparatus 710 according to a second embodiment of theinvention. The difference between the present embodiment and the firstembodiment is that the filter units 720_1-720_3 in the presentembodiment are assumed to be a histogram filter unit 720_1, a medianfilter unit 720_2, and a low-pass filter unit 720_3. The histogramfilter unit 720_1 obtains the most frequently appearing surroundingmacroblock as a filtering motion vector FMV_1 through histogramstatistic, the median filter unit 720_2 serves a median of surroundingmotion vectors as a filtering motion vector FMV_2, and the low-passfilter unit 720_3 averages the surrounding motion vectors to output afiltering motion vector FMV_3.

In addition, the difference between the control unit 740 (as shown inFIG. 8, which is a block diagram of the control unit 740 in FIG. 7) inthe second embodiment and the control unit 310 (as shown in FIG. 4A) inthe first embodiment is that the control unit 740 has N variationparameter calculation units 410_1-410_3 (in the present embodiment, N=3;however, the invention is not limited thereto), wherein the variationparameter calculation units 410_1-410_3 respectively receive thefiltering motion vectors FMV_1-FMV_3 to calculate variation parametersVP1-VP3. The operations and circuit structures of the variationparameter calculation units 410_1-410_3 are similar to those of thevariation parameter calculation unit 410 in the first embodiment, andthe difference is that the variation parameter calculation units410_1-410_3 in the present embodiment respectively replace the currentmotion vector MV0 of the variation parameter calculation unit 410 in thefirst embodiment by using the filtering motion vectors FMV_1-FMV_3. Thereplacement can be implemented by those skilled in the art and will notbe described herein.

As described above, the selector 850 in FIG. 8 determines the smallestone of the variation parameters VP1-VP3 (herein it is assumed that thevariation parameter VPi is the smallest, wherein i is a positive integerand 1≦i≦N) to obtain the filtering motion vector FMV_i most suitable forthe current macroblock and generates a control signal CS. Next,referring to FIG. 7 again, the multiplexer 730 selects and outputs themost suitable filtering motion vector FMV_i according to the controlsignal CS.

In summary, a motion vector refining apparatus provided by an embodimentof the invention calculates variation parameters of motion vectors andanalyzes block matching errors of macroblocks, so as to determinewhether an output image is at the edge of a moving object and adjust andrefine the motion vectors output by a plurality of filter unitsaccordingly. Thereby, when an image is at the edge of a moving object,the motion vector refining apparatus reduces the smooth intensities ofthe motion vectors (i.e., allows the motion vectors to have greatervariations). When the motion vectors require higher smooth intensities(for example, the macroblocks are not located at the edge of the movingobject), the motion vector refining apparatus adjusts and outputs motionvectors with higher smooth intensities, so as to reduce image defectscaused by a smooth processing.

Moreover, in an embodiment of the invention, a refined motion vector isoutput to a motion compensation unit to perform precise motioncompensation. The refined motion vector may also be provided to a motionestimation unit to allow the motion estimation unit to preciselyestimate the motion vectors required by an image.

It will be apparent to those skilled in the art that variousmodifications and variations can be made to the structure of theinvention without departing from the scope or spirit of the invention.In view of the foregoing, it is intended that the invention covermodifications and variations of this invention provided they fall withinthe scope of the following claims and their equivalents.

What is claimed is:
 1. A motion vector refining apparatus, comprising: acontrol unit, receiving a motion estimation signal generated by a motionestimation unit, wherein the motion estimation signal comprises aplurality of total motion vectors, the total motion vectors comprise acurrent motion vector corresponding to a current macroblock and aplurality of surrounding motion vectors, and the control unit calculatesa variation parameter according to the current motion vector and thesurrounding motion vectors to generate a control signal, wherein thecontrol unit comprises: N variation parameter calculation units, whereinthe ith variation parameter calculation unit performs a motion vectorcorrelation calculation by using the ith filtering motion vector and thesurrounding motion vectors corresponding to a plurality of neighboringmacroblocks around the current macroblock, so as to calculate an ithvariation parameter, wherein i is a positive integer and 1≦i≦N; and aselector, coupled to the variation parameter calculation units,determining values of the variation parameters to generate the controlsignal; N filter units, analyzing the total motion vectors by using Nanalysis processes to calculate N filtering motion vectors, wherein N isa positive integer and is greater than 1; and a mixer unit, coupled tothe control unit and the filter units, weighting and mixing thefiltering motion vectors according to the control signal to adjust andoutput a refined motion vector.
 2. The motion vector refining apparatusaccording to claim 1 further comprising: a buffer, coupled to thecontrol unit and the filter units, receiving and buffering the motionestimation signal.
 3. The motion vector refining apparatus according toclaim 1, wherein the motion estimation signal further comprises a blockmatching error corresponding to the current macroblock, and the controlunit comprises: a variation parameter calculation unit, performing amotion vector correlation calculation by using variations of the currentmotion vector and the surrounding motion vectors corresponding to aplurality of neighboring macroblocks around the current macroblock, soas to calculate a variation parameter; a reliability parameter analysisunit, receiving and analyzing the block matching error to generate areliability parameter, wherein the block matching error is an optimalresult generated by performing block matching on the current macroblockand a plurality of macroblocks of a next frame; and a value mixer,coupled to the variation parameter calculation unit and the reliabilityparameter analysis unit, mixing the variation parameter and thereliability parameter according to a mixing proportion to generate thecontrol signal.
 4. The motion vector refining apparatus according toclaim 3, wherein the motion vector correlation calculation is to performa sum of absolute difference (SAD) calculation or a variance calculationon the surrounding motion vectors by using the current motion vector. 5.The motion vector refining apparatus according to claim 3, wherein thecontrol unit further comprises: a motion vector buffer, receiving andbuffering the current motion vector and the surrounding motion vectors;and a reliability information buffer, receiving and buffering the blockmatching error corresponding to the current macroblock.
 6. The motionvector refining apparatus according to claim 3, wherein the blockmatching error is an optimal result generated by performing one of amean absolute difference (MAD) calculation, a SAD calculation, and avariance calculation on corresponding pixels in the current macroblockand the macroblocks of the next frame.
 7. The motion vector refiningapparatus according to claim 1, wherein the analysis processes of thefilter units are respectively N smooth intensities, and the smoothintensities are different from each other.
 8. The motion vector refiningapparatus according to claim 1, wherein the mixer unit adjusts Nweighted values according to the control signal and adds up a product ofthe ith weighted value and the ith filtering motion vector, so as togenerate the refined motion vector, wherein i is a positive integer and1≦i≦N.
 9. The motion vector refining apparatus according to claim 8,wherein when a value of the control signal increases, the mixer unitincreases the ith weighted value corresponding to the ith filter unithaving a low smooth intensity and decreases the ith weighted valuecorresponding to the ith filter unit having a high smooth intensity. 10.The motion vector refining apparatus according to claim 1, wherein thecontrol unit further comprises: a motion vector buffer, coupled to thevariation parameter calculation units, receiving and buffering thesurrounding motion vectors corresponding to the neighboring macroblocks.11. The motion vector refining apparatus according to claim 1, whereinwhen the selector determines that the ith variation parameter has aminimum value among the variation parameters, the selector controls themixer unit by using the control signal to output the ith filteringmotion vector.
 12. The motion vector refining apparatus according toclaim 1, wherein the mixer unit is a multiplexer, and the multiplexeroutputs one of the filtering motion vectors according to the controlsignal.
 13. The motion vector refining apparatus according to claim 1,wherein the filter units comprise: a low-pass filter unit, filtering thetotal motion vectors according to a low-pass filtering condition, so asto generate a low-pass filter vector; a median filter unit, calculatinga median of the total motion vectors and outputting a median filtervector corresponding to the median; and a histogram filter unit,counting the total motion vectors to output one of the motion vectorswhich has a highest appearance probability as a histogram filter vector.14. The motion vector refining apparatus according to claim 1, whereinthe refined motion vector is output to the motion estimation unit toadjust the total motion vectors.
 15. The motion vector refiningapparatus according to claim 1, wherein the refined motion vector isoutput to a motion compensation unit to perform a motion compensationoperation.